To get an accurate measurement, you need a rigid ruler or flexible measuring tape, full erection, and a consistent technique. The standard approach used in clinical studies is called bone-pressed erect length (BPEL), measured along the top of the penis from the pubic bone to the tip. Most men who search for this want a number they can trust, so getting the method right matters more than the tool you use.
How to Measure Length
Stand upright with a full erection. Place a rigid ruler or straight edge along the top (dorsal) surface of the penis. Press the end of the ruler firmly against the pubic bone, pushing into the fat pad above the base. Measure in a straight line from the bone to the very tip of the head. That number is your bone-pressed erect length, or BPEL, and it’s the measurement used in nearly all clinical studies on penile size.
Pressing to the bone matters because it removes the variable of body fat. Two men with identical penile anatomy can get different numbers if one carries more weight in the pubic area. By pressing through the fat pad, you get a measurement that reflects actual size regardless of weight fluctuations. This is why researchers standardized on it.
If you’d rather know what’s visible without pressing in, that’s called non-bone-pressed erect length (NBPEL). Same technique, but you rest the ruler gently against the skin without pushing. This gives you a shorter number but reflects what you’d see in the mirror. Think of BPEL as the structural measurement and NBPEL as the cosmetic one.
Measuring Without an Erection
If measuring erect isn’t practical, stretched flaccid length is a reliable stand-in. Meta-analyses have found that stretched flaccid length produces nearly identical results to erect length for most men. To do this, stand up, gently stretch the flaccid penis outward (parallel to the floor), and measure along the top from the pubic bone to the tip using the same bone-pressed technique. Pull firmly but not to the point of discomfort.
Unstretched flaccid measurements are much less useful. Flaccid size varies dramatically based on temperature, stress, physical activity, and time of day. A cold room alone can reduce flaccid length significantly. Stretched length controls for all of that by pulling the tissue to its functional limit.
How to Measure Girth
Use a flexible fabric measuring tape or a strip of paper you can mark and then hold against a ruler. Wrap it around the shaft at its widest point, which for most men is roughly halfway between the base and the head. This mid-shaft location is the standard. Don’t measure at the base, which tends to be thicker and will give you an inflated number that doesn’t match how girth is reported in studies.
Make sure the tape is snug but not compressing the skin. Read the number where the tape overlaps. If girth varies noticeably along the shaft, mid-shaft is still the default, but you can note measurements at multiple points if you want a complete picture.
Getting a Consistent Number
Ambient temperature and arousal level both affect rigidity, which directly affects your measurement. A warm room (around 77°F or 25°C) is what clinical settings aim for. Anxiety or distraction can prevent a full erection, and a partial erection will give you a shorter reading. If you’re measuring at home, pick a time when you can get fully aroused without rushing.
Take three measurements on different days and average them. Erection quality varies from session to session, and a single measurement can be off by a noticeable margin. Measuring along the top of the penis (not the side, not the underside) is critical for consistency, since the underside includes extra tissue near the base that inflates the number. Always measure in a straight line from base to tip, even if there’s a natural curve.
How Your Numbers Compare
A large meta-analysis pooling data from studies worldwide found the following averages: flaccid length of about 3.4 inches (8.7 cm), stretched flaccid length of 5.1 inches (12.9 cm), and erect length of 5.5 inches (13.9 cm). These are bone-pressed measurements. If you measured non-bone-pressed, your number will typically be a quarter to a half inch shorter, sometimes more depending on body composition.
Girth data is less centralized, but most studies report an average erect circumference in the range of 4.5 to 4.7 inches at mid-shaft. If your numbers fall within a reasonable range of these averages, you’re statistically normal. Size follows a bell curve, so the vast majority of men cluster within about an inch of the mean in either direction.
Why Measurement Matters Medically
Accurate self-measurement isn’t just about curiosity. Men with Peyronie’s disease, a condition involving scar tissue that causes curvature and sometimes shortening, need reliable measurements to track changes over time. Studies have found that subjective estimates of penile dimensions don’t correspond well with objective measurements, which means “it looks shorter” isn’t enough information for a doctor to work with. If you’re tracking size changes due to a medical condition, using the bone-pressed technique consistently gives you and your provider data you can actually compare visit to visit.
Condom sizing is another practical reason to measure. Length matters less here since most condoms accommodate a wide range, but girth determines whether a condom fits snugly or rolls off. A mid-shaft circumference below about 4.4 inches typically calls for a snugger fit, while anything above 5 inches benefits from a larger size. Getting girth right reduces the risk of breakage and slippage.